Generic higher order function

by

Here’s the inline magic.
Let’s take kvb’s code and define a single gmap function that handles all cases:

let inline gmap f (x, y) = f $ x, f $ y

type One = One with static member ($) (One, x) = 1  // Example1 ConvertAll
type Id  = Id  with static member ($) (Id , x) = x  // Example2 PassThrough

type SeqSingleton  = SeqSingleton  with static member ($) (SeqSingleton , x) = seq [x]
type ListSingleton = ListSingleton with static member ($) (ListSingleton, x) = [x]
type ListHead      = ListHead      with static member ($) (ListHead, x) = List.head x

// Usage
let pair1 = gmap One ("test", true)
let pair2 = gmap Id  ("test", true)
let pair3 = gmap SeqSingleton  ("test", true)
let pair4 = gmap ListSingleton ("test", true)
let pair5 = gmap ListHead (["test";"test2"], [true;false])

let pair6 = ("test", true) |> gmap ListSingleton |> gmap ListHead

(* results
val pair1 : int * int = (1, 1)
val pair2 : string * bool = ("test", true)
val pair3 : seq<string> * seq<bool> = (["test"], [true])
val pair4 : string list * bool list = (["test"], [true])
val pair5 : string * bool = ("test", true)
val pair6 : string * bool = ("test", true)
*)

UPDATE

It’s also possible to use the even more generic gmap function defined here then it will also work with n-uples (n < 9).

More Related Contents:

  1. Does F# have generic arithmetic support?
  2. Functions with generic parameter types
  3. How do I write this member constraint in F#?
  4. “Expected type parameter” error in the constructor of a generic struct
  5. Why doesn’t the example compile, aka how does (co-, contra-, and in-) variance work?
  6. Scala: Abstract types vs generics
  7. Why does a generic method inside a trait require trait object to be sized?
  8. Conflicting implementations of trait in Rust
  9. Use of `inline` in F#
  10. TypeScript: self-referencing return type for static methods in inheriting classes
  11. How do I return a Filter iterator from a function?
  12. Generic Functions in Go
  13. Why can’t I use a key function that returns a reference when sorting a vector with sort_by_key?
  14. How to cast an object to a list of generic type in F#
  15. Generic repository in ASP.NET Core without having a separate AddScoped line per table in Startup.cs?
  16. F# generics / function overloading syntax
  17. Why can’t `&(?Sized + Trait)` be cast to `&dyn Trait`?
  18. How to write a function for generic numbers?
  19. Can I avoid eager ambiguity resolution for trait implementations with generics?
  20. Difference between “*” and “Any” in Kotlin generics
  21. What does the question mark mean in a type parameter bound?
  22. Calling a static method from a generic constraint Dart
  23. Generic NSOperation subclass loses NSOperation functionality
  24. Extension of constructed generic type in Swift
  25. How to get actual type arguments of a reified generic parameter in Kotlin?
  26. What does it mean to instantiate a Rust generic with an underscore?
  27. Unable to create a polymorphic type because the trait cannot be made into an object
  28. What is the cited problem with using generic type parameters in trait objects?
  29. How to call a named constructor from a generic function in Dart/Flutter
  30. Returning original collection type in generic method

Leave a Comment